An Ennead is a group of nine deities worshipped by which ancient civilisation?

The Ennead or Great Ennead was a group of nine deities in Egyptian mythology worshiped at Heliopolis: the sun god Atum; his children Shu and Tefnut; their children Geb and Nut; and their children Osiris, Isis, Set, and Nephthys. The Ennead sometimes includes the son of Osiris and Isis, Horus.

The Great Ennead was only one of several such groupings of nine deities in ancient Egypt. According to the creation story of the Heliopolitan priests, the world originally consisted of the primordial waters of precreation personified as Nun. From it arose a mound on the First Occasion. Upon the mound sat the self-begotten god Atum, who was equated with the sun god Ra. Atum evolved from Nun through self-creation. Atum either spat or masturbated, producing air personified as Shu and moisture personified as Tefnut. The siblings Shu and Tefnut mated to produce the earth personified as Geb and the nighttime sky personified as Nut.

Geb and Nut were the parents of Osiris and Isis and of Set and Nephthys, who became respective couples in turn. Osiris and Isis represent fertility and order, while Set and Nephthys represent chaos to balance out Osiris and Isis. Horus, the son of Osiris and Isis, is often included in this creation tradition.